Suspension New Member Project 2023

Instructions: You are designing the front double-wishbone suspension for a solar car. Due to packaging concerns, you have decided to use a pushrod-bellcrank assembly to store the shock absorber on top of the frame. However, you want the motion ratio of the assembly (the amount that the shock moves over the amount that the wheel moves) to match that of the rear suspension. You know that the rear motion ratio is around 1:1, which is a desirable motion ratio to have for a racecar.

First, you should use VSUSP to design your desired suspension geometry. It is always good to get your ideas down on paper (or iPad). Next, begin modeling your components. Take care to model them so that they are compatible together. Hint: since ideal wishbone behavior is roughly 2-D on the yz-plane, you can plan out your geometry using a 2D sketch and line components! From there, I want you to create an assembly integrating your components together. If things don’t fit quite right, feel free to go back to the drawing board

Suspension Properties to Follow:

Frame Width: 498 mm
Frame Height: 315.84 mm
Tube Width: 25.4 mm
Desired Zero-Bump Camber: ~0, slightly negative
Desired Camber Gain Rate: -0.6 - -0.8 deg camber/ deg body roll

VSUSP Baseline Link

Parts to Model:

Upper and lower wishbone
Pushrod
Bellcrank

Parts to Find:

Hardware components: rod ends, bearings, bolts, nuts, etc
Shock absorber (given)
Frame tabs (given)

As an additional challenge, I would like y’all to investigate modeling tube wishbones. This is because they are much simpler to manufacture and can be iterated quickly. When doing so, it is important to be deliberate with how you implement them. (Hint: look up “rod end in bending”). If you want even more of a challenge, you could look at implementing skeleton modeling. This is where you have a master reference sketch with all geometrical dimensions for your dynamics system defined, after which you reference this sketch in all assemblies. This is optional though since we are going to try and implement this system wide next semester, but if you want to get a head start, feel free to do so.

I will provide a model for the shock absorber, but I will not provide a model for the upright. It is up to you to geometrically constrain the wishbones so that they move correctly within the assembly as if the upright was there.

Each of you is to model your own assembly. You may collaborate with regard to design, but all specific CAD work must be your own. This is to build your CAD skills and build your intuition on how to translate a theoretical design into an actual model.

This is a very challenging first member project. It has parts of every step of the engineering design process except for manufacturing. Do not hesitate to use all online resources available. Additionally feel free to message your suspension lead, dynamics lead, mechanical lead, or chief engineer with any questions about literally anything. We are here to help. The purpose of this project is to “push you in the pool,” so to speak, with regard to suspension theory and design. I hope this project does a lot to build your suspension design knowledge and CAD proficiency!

Due date: Saturday, October 7th

Have fun! 😁